Treatment of lubricating oil



Patenteddune 19, 1945 2,378,762 TREATMENT F LUBRICATING 'IL l Frederick E. Frey, Bartlesville, om., assigner to Phillips Petroleum Company, a corporation of Delaware Application December 4, 1942, Serial No. 467,875 Claims. (Cl. 196-39) Lubricating oils of high quality have been manufactured from crude oil fractions having suitable boiling ranges by many processes, including sulfuric acid rehning, aluminum chloride rening,

and solvent extraction. In sulfuric acid or aluminum chloride processes, the treating reagents are consumed by reaction with the oil and are not economically recoverable from the resulting sludges. In solvent refining, the action is simply one of separating high-quality lubricating ingredients from the crude oil, or removing the undesirable or low-quality constituents; thus the yield of finished lubricating oil can'be no greater than the proportion of lubricating oil-grade hydrocarbons in the raw material.

An object of this invention `is to produce highquality lubricating oil in high yield by a chemical process in which the chemicalreagent is recoverable.

Another object of this invention is to convert paraffin wax to normally liquid hydrocarbons suitable for blending in lubricating oil.

Another object of `this invention is to improve cating oil.

`cyclic materials for use as ingredients in lubri- Another object is to combine advantageously,

into a process for manufacturing lubricating oil, steps for treating oil stocks with hydroiiuoric acid with steps for solvent refining of the oil stocks.

Other objects and advantages of this invention will be apparent to those skilled in the art from the following description, the accompanying drawing, and/or the appended claims.

According to this invention, a lubricating oil stock is treated with concentrated or substantially anhydrous liquid hydrofiuoric acid under conditions selected to improve or modify the properties ofthe oil. Properties which may be changed include one or more of the following: viscosity or viscosity index, ilash and fire points, pour point, and carbon residue. These changes are preferentially promoted by carrying out the reaction in the presence of solvents or diluents such as lowboiling normally liquid hydrocarbons or halogenated hydrocarbons, in the presence of added alkylating agents, such as olens or polymers of oleflns having 2 to 5 carbon atomsper molecule, or in the presence of catalyst modifiers, such as boron fluoride, sulfur trioxide, phosphoric anhy' dride, halides of antimony, arsenic, bismuth, or

tin, zirconium, or other metals selected from the third and fourth periods of the periodic table.

The exact nature of the chemical changes which occur inthe treatment are not known. It is presumed that a lnumber of reactions occur simultaneously and that the nature and the extent of the predominating reactions are influenced appreciably by varying the conditions of temperature and pressure and by the use'of solvents, alkylating agents, catalyst modifiers, and the like. As disclosed in the aforementioned copending application, paraillnic hydrocarbons in the presence of concentrated hydroiiuoric acid undergo extensive reconstruction to lowerand higher-boiling hydrocarbons and also to one or more hydrocarbons having the same number of carbon atoms but different carbon-skeletal structure. Alkylation probably occurs to some extent if alkylating agents are present in the reaction mixture, particularly when aromatic ring compounds are present as components in the oil being treated. Highboiling oleflnic hydrocarbons may undergo reactions such as cyclization to naphthenes', depolymerization, isomerization, or disproportionation to parafns and diolens or aromatica. `Aromatics may undergo condensation reactions with added alkylating agents, such as ethylene, propylene, halogenated hydrocarbons, alcohols, and the like. Sulfur, nitrogen, and oxygen compounds in the lubricating oil may be simultaneously removed by absorption in, or formation of loose compounds with, the hydrouoric acid. The presence of boron fluoride, sulfur trioxide, phosphoric anhydride, or the like, appears to increase the catalytic activity and the selective vsolvent, `power of the hydrofluoric acid. Boron fluoride is par- )ticularly eifective when in concentration of 1 to 5 'per cent. The nature of the effects is also dependent upon the nature of the lubricating feed stock.

Treatment of lubricating oil stocks with hydroiiuoric acid under relatively mild conditions of temperature and time, such as 50 to 250 F. and for a time of 1 to 30 minutes, ordinarily raises the viscosity index, increases the API gravity slightly, improves the color, and raises the pour point slightly; it usually does not change the absolute viscosity greatly. Under relatively drastic conditions, such as at a temperature in the range 'of 300 to 450 F., or with a Contact time of one or more hours, the absolute viscosity decreases substantially. The extent of reaction is controllable to some degree by limiting the proportion of hydroiluoric acid used in the treatment. That is, hydrogen fluoride tends to form molecular complexes and addition compounds with some of the more reactive or less stable hydrocarbons dissolved salts or` colloidal suspensions of the folllowing metals: silvernickel, cobalt, chromium,

found in lubricating oil, and if the proportion of hydroiluoric acid is limited, 'say to from 5 to about 50 per cent by weight of the lubricating oil being Asphalt Resins Naphthenes Cyclo-alkyl compound Paraiilns, including wax Color bodies Asplaltic constituents are tarry or pitchy materials of aromatic structure. Resins are similar y but of lower molecular weight and more soluble in parain hydrocarbons. These constituents cause sludge and varnish formation in motor oils, and therefore must be -removed by oil-refining processes.

By naphthenes is meant saturated liquid hydrocarbons which are predominantly cyclic in structure. y eating properties for use at constant temperattures, but the viscosity index is low; that is, the viscosity varies greatly with the temperature. Consequently, only a limited proportion may be present in lubricating oil of high viscosity index.

The cyclo-alkyl compounds are hydrocarbons having one or more cyclic nuclei with long aliphatic chains attached thereto. These compounds are the preferred pedominant constituents of lubricating motor-oils for general use. The viscosity index is high; thepour point is low; the carbon-forming tendency is low; and the oils are stable against oxidation.

The parains have very high viscosity indices, and good lubricating properties. However, the carbon-forming tendency is greater than for cycloalkyl compounds. As many of the parafllns present in lubricatingoil stocks have high melt'- ing points, the proportion ofparaiiins which may be present in the final lubricating oil is limited lmainly by the maximum permissible pour point of the oil. The allowable proportion of paramns may be increased somewhat by using pour point depressants.

The structure of the color bodies isI not fully known. They are objectionable mainly because of consumer demand for oil of clear and standard appearance.

Concentrated hydrofluoric acid has both a solvent eiect and a chemical effect upon the lubrieating oil. By its solvent effect, it dissolves as- Such hydrocarbons have good lubriform resins and asphaltic compounds. .Aromatics Thus concentrated hydrouoric acid may be used I similarlyt to a single solvent in a series of solvent extraction steps at progressively higher temperatures to fractionate" lubricating oil stocks into extracts of progressively increasing "parafllnlcity or hydrogen-to-carbon ratio. There are always some chemical reconstruction reactions of the more reactive. of the ingredients, though if deslred these may be retarded by the use oi short contact times.

The yiency of the extraction o1 cyclics and the like'fr `m lube oil stock by concentrated hydrouoric acid may be greatly increased by concurrently using a deasphalting diluent or selective solvent which is immiscible with hydroiluoric acid. Liquid propane is a preferred diluent. That is, at temperatures in the range of about 50 to 200 F., propane dissolves paraillns and cycloalkyl hydrocarbons in lubricating oil, but precipitates substantial proportions of asphaltic and resinous materials. lThus the use of propane as a diluent for treating lube oil stocks with hydrouoric acid greatly increases the selective solvent power of the acid for removing asphaltic, resinous, and aromatic constituents from the oil. Other low-boiling hydrocarbons such as ethane, butane, pentanes, or mixtures are also advantageous in some instances. For example, in car- Vrying out the treatment at high temperaturesA such as 200 to 450 F., butane. pentanes, or even higher-boiling parans are advantageous because lower pressures may be used than with propane. Next to propane, butane is preferred. l

Thechemical effect of hydroiluoric acid on asphaltic constituents appears to be slight. Resinforming substances are probably condensed to and naphthenes appear to be substantially unaffected except in the presence of alkylating agents phaltic, resin-forming, and other cyclic hydrocarbons preferentially to cycloalkyl and parallinic hydrocarbons.

The extent of the solvent eect is dependent upon the temperature, the pressure, the proportion o f hydroiluoric acid, and the presence or absence of another solvent. For example, at room temperature, asphaltic, aromatic, unsaturated, and naphthenic hydrocarbons are appreciably soluble in concentrated hydrouoric acid, whereas parailinic and cycloalkyl hydrocarbons, or hydrocarbons of high hydrogen-to-carbon ratios, are substantially insoluble. As the temperature is increased, the solvent power of concentrated hydroiluoric acid increases until at labout 350 F. and two thousand pounds per square inch pressure theV acid is almost completely miscible with cyclics, and under these conditions it will dissolve substantial proportions ot the parafns.

or under drastic conditions oi time and temperature'. In the presence of alkylating agents, they appear to be converted in part to compounds of greater parail'inicity, presumably by addition oi.'

aliphatic side chains to the cyclic structures. At high temperatures some of the cyclics probably react -wlth high-molecular-weight -parafllns to form cyclo-alkyl hydrocarbons and corresponding lower-molecular-weight parains. Cyclo-alkyl compounds appear to be comparatively stable and unaiected by hydroiluoric acid, although some molecular rearrangements may occur at high temperatures. Parailns are broken down to lower-molecular-weight compounds in high-temperature treatments, and if low-molecular-weight aromatics, such as benzene or naphthalene, are present, alkyl aromatics may beformed 'in appreciable proportions.

The treatment given a speciilc lubricating oil stock depends in large measure upon the nature of the stock. Paramn-base cruies, such as are found in Pennsylvania oils,'req ire 9, treatment which removes paraiin wax or converts part of it to lower-melting materials; that is, the pour point of the o il must be decreased by the refining process. Asphalt-base crudes, such as, are-found in- California and along the Gulf Coast, require a treatment which removes asphaltic, resinous, and

'naphthenic components or converts them to masuch as are found in Oklahoma, Kansas, and Il,

. linois, require treatment to remove unstable easily oxidizable or varnish-forming constituents and to modify the pour point and viscosity index. y

m `treating parafIln-base crudes according to the principles of this invention. it is usually desirable to add some unsaturated cyclic materials, such as benzene, terpenes, and the like, to the oil prior to or during contacting with hydroiluoric acid. The added cyclic compounds react in the presence of hydrofluorlc acid with part of the high-molecular-weight` parains or waxes of the oil to produce highly desirable cyclo-alkyl compounds and paraiins of relatively low molecular weight. This decreases the pour point of the oil without excessively decreasing the viscosity index and produces a maximum yield of reilned lubricating oil.

In treating asphalt-base crudes according to the principles of this invention, it is desirable to add aliphatic alkylating agents, such as oleins, cracked gasoline, alcohols, or alkyl halides, to the oil prior to or during contacting with hydrofluoric acid. The added alkylating agents react in the presence of hydrofluoric acid with naphthenic and aromatic constituents of the oil to produce compounds of increased paramnicity or hydrogento-carbon ratio. This increases the viscosity index of the oil and gives a much higher yield of refined oil than solvent extraction methods, which simply remove naphthenic vcomponents from the ,crude oil.'

In treating mixed-base crudes, it may some-- times be desirable to add alkylating agents, depending upon whether the properties of the speciilc crude treated approach those of paraninbase crudes or of asphalt-base crudes. In general, a simple treatment with hydrofluoric acid in the presence of a solvent, followed by a decolorizing, and in some cases a dewaxing, step gives very satisfactory results.

Understanding of some aspects of my invention may be aided by referring to the accompanying drawing, which is a schematic flow diagram of one. preferred arrangement of apparatus for practicing my invention. In this specific embodiment of my invention, propane is used to dilute the lubricating oil and to aid the acid in separating asphalt and wax from the oil. In some instances it is desirable to use an isoparaflin `such as isobutane or isopentane, for such isoparaiilns at relatively low temperatures `will react with unsaturates in the oil in the presence of hydroiluoric acid to produce saturates, and at relatively high temperatures will react with high-melting parafflns to produce relatively low-melting paramns.

Liquid propane and crude lubricating oil are admitted, as through inlets I and II, respectively, to mixer I2, in which they are mixed together at a deasphalting temperature. In some modifications' of this invention, especially for treating parafln-base crudes, it will be desirable to use a cyclic hydrocarbon, such as benzene, as the solvent or as one component of the solvent; for treating most mixed-base and asphalt-base crudes, low-,boiling paraiiins,` such as` liquid propane, appear to be the most suitable solvents. One distinct advantage in using propane as the solvent results from the fact that hydrogen fluoride is soluble in liquid propane to the extent of several per cent at temperatures only slightly above room temperature. This facilitates contacting of the oilIWith the acid. The optimum temperature depends to some extent upon the nature of the feed stock but is usually in the range of about 50 to 200 F. In general, asphaltic and resinous constituents are less soluble in propane at high temperatures than at low. The pressure should be suiilcient to maintain substantially all the propane in the liquid phase and will generally be in the range of 100 to 600 pounds per square inch or more. The propane-to-oil ratio may rangefrom 2:1 to 10:1 by weight. Generally a ratio in the range of 2.5:1 to 5:1 is preferred. At lower ratios the diluting and deasphalting action of propane is relatively inefilcient, whereas at higher ratlosthe quantity of propane being handled may be excessive. Under the preferred conditions mentioned, propane dissolves substantially all of the lubricating oil constituents except asphaltic and resinous substances.

From mixer I2 the mixture passes to asphalt settler I3, wherein asphaltic and resinous materials settle out and are removed through outlet Il. The temperature may be reduced somewhat in settler I3 by allowing part of the propane to evaporate and to be removed as vapor through conduit I5. i

From settler I3 the resulting deasphalted mixture is transferred by pump I6 through conduit II'to treater I8. In treater I8 it is agitated with concentrated or substantially anhydrous hydrofluoric acid which may be introduced` through inlet I9 and/or recycle conduits 20 and 2l. Treater I8 may be operated at a temperature in the range of about 50 to about 450 F. The exact temperature chosen in a particular instance will depend upon the characteristics of the crude oil, the solvent eiect desired, the chemical effect desired, and the proportion of hydrofluoric acid used. In most instances the preferred temperature is in the range of 100` to 300 F. In general, at the lower temperatures within the operative range, unstable constituents such as unsaturated compounds, organic acids, resinor sludge-forming materials are extracted by solution in the hydroiluoric acid; in the absence of alkylating agents, the other con.. stituents may undergo some molecular rearrangement and reconstruction reactions but, as a whole, are not greatly changed. If an alkylating agent, such as an olefin, a nonprimary alkyl halide, or a nonprimary alcohol, is present, considerable reaction occurs, and the yield of lubricating oil may be greatly increased. The alkylating agent appears to react preferentially with cyclic compounds and with cyclic groups in cyclo-alkyl cornpounds, thereby increasingthe parafnicity or hydrogen-to-carbon ratio of these compounds, reducing their solubility in hydrouoric acid, and rendering them more suitable as constituents in lubricating oil.

At the higher temperatures within the operative range, hydrofluoric acid in large proportions extracts substantially all of the aromatic compounds and considerable proportions of the nonaromatic cyclic compounds. `It may also cause extensive chemical reconstruction of the remain- 4 ing compounds if the reaction time is sufllciently long. Part of the aliphatics or waxes are converted to compounds of lower molecular weight.

`Waxes may react with low-boiling aromatics, such as benzene, naphthalene, anthracene, and the like, to produce normally liquid alkyl aromatics, which act to decrease the pour point of the lubricating oil. For this reason it is advantageous in some instances, for example when the crude oil contains relatively large proportions of wax or has a relatively high pour point, to add a lowboiling aromatic to the reaction mixture. At temperatures above about 200 F., ethylene, primary alcohols, and primary alkyl halides may be used as alkylating agents.

The proportion of hydrofiuoric acid in the mixture may vary from about 0.1 to 10 parts or more by weight per part of the crude oil, depending upon the nature ofthe crude oil and the desired characteristics of the refined oil. For producing high-grade motor lubricating oils from average lubricating oil stock, the optimum proportion of acid usually is in the range of about 0.5 to 4 parts by 4weight per part of the crude oil. By treating the oil with several relatively small successive portions of hydrofluoric acid, the effect is substantially that of a selective solvent; that is, the relatively unstable compounds form complexes with the acid which dissolve in the acid phase, and the relatively stable constituents are substantially unaffected. When a large excess of hydroiluoric acid over that required to tie up or remove, as compounds or molecular complexes, most 'of' the unstable or undesired constituents is used,

and when a suillclent reaction time is allowed, the relatively stable acid-insoluble lubricating oil constituents undergo considerable chemical change as already described.

'I'he reacted mixture from treater I8 is passed through conduit 22 to cooler 23, wherein by flash evaporation of part of the propane and hydrogen fluoride from the mixture, the remainder is cooled to the desired separating temperature. The separating temperature determines the extent of the solvent action of the acid. The optimum temperature is usually in the range' of 50 to 300 F. though at times it'may exceed thisrange in-either direction. At low temperatures, such as 50 F., only the unsaturated compounds, aromatics, and nitrogen, su1fur, and oxygen-containing compounds dissolve appreciably in the acid.

At high temperatures, such as 300 F., and above,

substantially all aromatics and substantial proportions of nonaromatic cyclic compounds are extracted by, and removed in, the acid phase.

Vapors from cooler 23 are condensed and recycled through conduit 24 and pump 25 to treater I8. Liquids are passed through conduit 26 to separator 21, wherein they are separated .by centrifugal or gravitational means at the desired separating temperature into two-.liquid phases. In instances when only a relatively minor proportion of hydrogen fluoride is yused in treater I8, separator 21, may be by-passed--all hydrogen fluoride being flashed or distilled overhead and -recycled from cooler 23 and/or fractionator 29.

. The upper or hydrocarbon phase from separa- Y tor' 21 is passed through conduit 28 to fractionating column 28. Substantially all the dissolved hydrogen fluoride in the mixture is withdrawn as asvavea that, in -order to obtain an oil of given pour point,

the dewaxing temperature should be in the range dewaxed oil is passed through conduit 33 to decolorizer 39, in which it is subjected at a suitable temperature to the action of a contact mass having catalytic properties for hydrogenation and/or dehydrogenation at relatively higher temperatures, such as nely divided nickel, bauxite, etc.

Decolorizer '38 may consist of a conventional bauxite or clay treater/such as is well-known in the art of refining lubricating oil. Preferably it b is a bauxite filter bed. The propane-oil mixture is allowed to percolate through the bauxite at a temperature in the range of about 50 to 500 F.

. The most eflicient decolorization usually occurs an overhead azeotropic mixture of propane and hydrofluoric acid and is condensed and recycled through conduit 24. and pump 25 to reactor I8.

The resulting hydrogen fluoride-freed hydro'- carbon mixture is passed through conduit 30 to deasphalting unit 3|. The deasphalting unit consists essentially of a means for adjusting the temperature of the propane-hydrocarbon mixture and allowing the asphalt to settle out. The deasphaltingtemperature may be in the range of about 'l0 to 200 F., depending upon the degree of deasphaltingdesired. Asphaltic" and resinous substances may be withdrawn through outlet 32, and the' deasphalted hydrocarbon mixture is passed through conduit 33 to dewaxing unit 34.

In dewaxing-unit 34, the propane-oil solution is chilled slowly to a temperature in the range of about to 70 F., whereupon wax crystallizes out. The wax is then removed by known means, such as centrifugation or filtration. The purpose of dewaxing is mainly to reduce the pour point of the oil to a desired value. Experience has shown ration of phases.

at temperatures in the range of tai-300 F. In the decolorizing step, organically combined fluorine is also substantially completely removed.

The resulting clear, fluorine-free, dewaxed, and

deasphalted propane-oil mixture is passed through conduit40 to depropanizer 4I. In de.. propanizer 4I the oil is freed from propane by distillation: the propane is recycled through conduits 42 and 35 and pump 36 to mixer I2.l Lubricating oil of high'viscosity index,low pour point, and low carbon-forming qualities lis withdrawn through outlet 43; If desired, it may be fractionated, as by vacuum distillation, into several cuts of different viscosity, or-it may be blended with other lcils to modify its properties.

'I'he heavier or acid layer from separator 21 Imay be recycled in part through conduit 2| to treater I8; preferably a substantial proportion is passed through conduit 44 to column 45, and a proportion of about 1 to 5 times the weight of wax available for the presently described conversion to a pour point depressant is passed through conduit 46 to reactor 41.

In reactor 41 petroleum wax, such as that produced in dewaxing unit 34, is agitated with substantially anhydrous hydrofluoric acid (such as the used acid from separator 21) and one or more unsaturated or aromatic compounds, such as benzene, naphthalene, alkyl benzenes, alkyl naphthalenes, cycloolens, terpenes, and the like, added through inlet 62. The temperature may be from about 150 to about V450 F. Preferably it is in the range of 250 to 350 F. At low temperatures the rate of reaction is low, whereas at high temperatures excessive cracking occurs.`

The mixture should be continuously agitated to insure intimate contacting and to prevent sepa- -weight cyclic compounds having double bonds,

such as aromatics, cyclooleflns, terpenes, and the like, to produce cycld-alkylcompounds, consisting "of cyclic nuclei with one or more attached allwl groups, and paratlins of a molecular weight The pressure should be suiiilower than that of the original wax. If desired a dlluent or solvent, such as light naphtha or propane, may be used in` reactor 41 to reduce the viscosity of the mixture and to facilitate handling it.

The mixture from reactor 41 passes through conduit 48 to separator 49, in which it is separated, by cooling and centrifugal or gravitational means, into two liquid phases. The lighter or hydrocarbon phase is passed through conduit 50 to fractionator From fractionator 5| an overhead fraction, comprising unreacted lowmolecular-Weight reactants, diluents or solvent, and hydrogen fluoride, is recycled via conduct 52 t0 reactor 41. The bottom fraction, which consists mainly of cyclo-alkyl hydrocarbons having long alkyl groups, is withdrawn through outlet 53. This fraction is' suitable for use as a pour-point depressant in lubricating oils. K

The lower or acid layer from separator 49 is passed through conduit 54 to column 45. Column 45 is operated with a high enough kettle temperature, preferably in the range 300 to 500 F., to split out substantially all organically combined iiuorine as hydrogen fluoride. This hydrogen fluoride, any water incidentally introduced into the process, and a substantial proportion of the hydrocarbons present pass overhead through conduit 55 to column 56. oil is withdrawn through outlet 51.

.Column 58 separates hydrofluoric acid and Water, which passes overhead through conduit 58 to acid-rerun column 59, from hydrocarbons, which may be withdrawn through outlet 60. These hydrocarbons are liquid, of a clear color, have a low pour point, and are suitable for blending in small proportions with other lubricants.

Column 59 separates a constant-boiling mixture of water and hydrogen fluoride, which may be withdrawn through outlet 6|, from substantially anhydrous hydrogen fluoride, which is recycled through conduit 20 to treater I8.

To further illustrate some of the many aspects of this invention the following specific example is given.

Example l To a steel reactor having a mechanical stirrer were charged 0.48 pound of a mixed-base lubricating oil, 2.09 pounds of substantially pure hydrogen fluoride, and 0.75 pound of normal pentane.

rI'he mixture was agitated for one hour at 185 F. and then was separated into two phases. The hydrocarbon phase was washed free of hydrogen fluoride and was topped to 293 F., chiefly to remove the pentane. The remaining hydrocarbon was equivalent to 84.8 per cent by weight of the original oil. Part .of this material was tested by conventional lubricating oil tests. Another part was clay-treated by agitating it with fullers earth and filtering; it Ywas then also tested by conventional lubricating oil tests. The following test data were obtained:

From these data it is evident that the treat- A high-boiling residue ment increased the viscosity index of the oil, reduced the carbon-forming tendencies, and improved the color. The increase in pour point indicates an` increase in paraflin content and a corresponding decrease in naphthenes.

This invention is broadly applicable to many modified processes for reflning oils. It may be applied to the refining of various grades of crude oil, including paramn-base crudes, mixed-base crudes, and asphalt-base crudes. It may be used for producing any grade of oil, including such highly refined oils as transformer oil. It may be used advantageously in combination with older methods of reiining, such as solvent refiningl and sulfuric acid refining. It may be particularly advantageously combined with propane deasphalting and dewaxing steps, whereby the propane also serves as a diluent in steps for treating the oil with hydroiiuoric acid. It may be used in conjunction with alkylating agents to change appreciably the chemical constitution of the oil. Further, highly parafdnic lubricating oil fractions, such as petroleum waxes, may be converted in the presence of concentrated hydrofluoric acid and cyclic hydrocarbons to hydrocarbons of lower pour point and better adaptability for use as constituents in lubricating oil,

Because the invention may be practiced otherwise than as specifically described or illustrated,

and because many modifications and variations within the spirit and scope of it will be obvious to those skilled in the art of treating lubricating oil stocks, the invention should not be unduly rel. The process" of improving a lubricating oil stock having naphthenic and aromatic constituents which comprises contacting said stock dissolved in a low-boiling liquid parafn as a solvent with substantially anhydrous liquid hydroiiuoricl acid in the presence of an added aliphatic alkylating agent under conditions such as to cause said hydrofluoric acid to substantially improve said stock and cause said alkylating agent to react with said naphthenic and aromatic constituents i'nsaid stock to produce compounds of increased hydrogen-to-carbon ratio, separating the resultlng mixture into two liquid phases, namely, a hydrocarbon phase and an acid phase, separating said phases, and recovering the improved lubricating oil stock from said hydrocarbon phase.

2. The process of improving a paraflin-base lubricating oil stock which comprises contacting said stock dissolved in a low-boiling paraifln as a solvent with substantially anhydrous liquid hydrofluoric acid in the presence of an added unsaturated cyclic compound under conditions such as to cause said hydrofluoric acid to substantially improve said stock and cause said unsaturated cyclic compound to react with high molecular weight paraiiins in said stock to produce cycloalkyl compounds having pour-point depressant properties, separating the resulting mixture into two liquid phases, namely, a hydrocarbon phase and an acid phase, separating said phases, and recovering the improved lubricating oil stock from said hydrocarbon phase.

3. The process of improving a lubricating oil stock having paraiflnic, naphthenic and aromatic constituents which comprises contacting said stock dissolved in a low-boiling liquid paraffin as a solvent with substantially anhydrous liquid hydrofluoric acid in the presence of an added alkylating agent under conditions such as to phases, and recovering the improved lubricating cause said hydrouoric acid to substantially imoil stock from said hydrocarbon phase.

prove said stock and to cause said alkylating agent' 4. The process of claim 1 in which the lowto react with said stock to improve the lubricat-` boiling liquidl paraffin solvent is propane.

ing properties thereof, separating the resulting -5 5. The process of claim 2 in which the lowmixture into two liquid phases, namely, a hydroboiling liquid paraffin solvent is propane.

carbon phase and an acid phase, separating said FREDERICK E. FREY. 

